I would like to understand what will be the cost to build (bring
online) and maintain a website that provide the feature set like:
?	A site accessible on internet to any user 
?	Ability to do user registration 
?	Ability for any registered or non registered user to upload project
(single or multiple files)
?	Ability to capture additional information (attributes) about the
uploaded project
?	Ability for uploaded files to go thru a review and approval process
before it becomes available to general user
?	Ability for anyone (non registered user) to search the associated
information about the project
?	Ability for anyone (non registered user) to download the project files 
?	Ability to provide premium services (extended search and filtering,
email notification etc) for fee based account
?	Message board etc. 
?	Some news feeds 
?	Advertisement
One of the example sites that come very close is www.sourceforge.net 
 
Questions are, for above functionality or something close:
?	Is this feature set available in some Open Source/Free Software
project? What are they, the links and the typical licenses, cost if
any?
?	Are there any software tools/product that are commercially available
that provide this feature set? Sourceforge.com is potentially the one,
what are others? Is there some customization required? What will be
the typical cost of basic (off the shelf) or customized product?
?	Are there any online services (ASP) available that will brand the
solution for a particular company? If yes, who are they and what is
the associated cost?
?	If this needs to be custom build what will be the typical cost and
time frame? What will be the best means to get this done?
?	Assuming 100 project of 50 files each or 1000 projects of 5 files
each, where each text file contains about 300 - 700 lines or the
graphic files which are simple gifs, total project size about 1-2 MB.
What will be the typical cost of hosting and maintaining this site?
Thanks

I think Plone will do most of what you want. It's also open source.

Sourceforge has hundreds of possible packages listed at
http://sourceforge.net/softwaremap/trove_list.php?form_cat=243

Owain

If Plone isn't what you look for then may be you have to custom built
the application. Typicall such application will take 4 month to
complete and cost would be between US $10,000 to $45,000. But if you
outsource same to IT companies in India, Pakistan, etc the cost would
be max US $7,000.

Check google for "offshore software development companies" or try www.machsol.com.